This invention relates to a tone generator used in an electronic musical instrument.
There is a prior art digital type tone generator which uses a variable frequency dividing circuit such as disclosed in U.S. Pat. No. 3,824,397 specification. In this type of tone generator, variable adjustment of the pitch of a frequency divided output (i.e., a generated tone) is made by varying the frequency of a master clock pulse. For this purpose, the oscillation frequency of a master clock pulse oscillator is variably controlled by adjusting resistance value of a variable resistor or the like. This method of adjustment, however, is found to have a disadvantage of adversely affecting stability and accuracy of the frequency.
If it is desired to impart a vibrato effect to the generated tone, such vibrato effect can be produced by changing the master clock pulse frequency by a vibrato frequency. It is, however, difficult to change the master clock pulse frequency which is produced at a high rate in the order of 2MHz without impairing stability of the frequency.